That's the uncomfortable question swirling this week around the uber-trendy, Los Angeles-based chain that has attracted legions of calorie-counting, yoga mat-toting devotees and spawned a spate of imitators.

"Crackberry" addicts, prepare for your favorite dessert to take a licking from California Department of Food and Agriculture officials. Their answer:

Nogurt.

"You can't call a product frozen yogurt unless it's mixed off-site and delivered to the site as frozen yogurt," said Steve Lyle, a department spokesman.

Pinkberry executives concede that their product is made with a powder and mixed in-store. They say it includes plain yogurt, yet they wouldn't disclose what else goes into their refreshingly tart treat.

But a lawsuit might force them to take their secret recipe out of the deep freeze.

This week, a civil suit was filed in Los Angeles County Superior Court by L.A. resident Bryan Williams, 48, who contends that Pinkberry's powdered mix lacks the "good" bacteria cultures found in yogurt.

"For lack of a better word, it's just dessert," said Williams' attorney, Michael Amir. "We're just asking for them to ... tell the public the truth."

Williams, a legal recruiter who lives in West Hollywood, could not be reached for comment, but Amir says his client is a health-conscious guy with no affiliation to any Pinkberry competitor.

Mary Glarum, another attorney for Williams, said: "We're not asking for punitive damages.... The goal is to just have them come clean about what they're doing so that people can make an informed decision when they buy the product."

But Pinkberry founders -- who now have 15 California franchises and three in New York -- say they are "under attack" by imitators. The suit, they say, is just the latest salvo from a slew of bitter rivals.

Pinkberry "is yogurt, absolutely 100%" vowed company President Young Lee, who said he's working with the state to resolve the concerns. "We are more frozen yogurt than other frozen yogurt."

If Lee is a little defensive, and protecting the recipe as if it's a state secret, it's because Pinkberry has caused its fair share of controversy since its first outlet opened in 2005, serving just two flavors: plain and green tea.

Within a year, the tiny West Hollywood shop was drawing 3,000 customers a day, most of them self-described Pinkberry addicts willing to risk parking tickets to stand in a line that snaked around the block. Neighbors wanted Pinkberry to move, but the city negotiated a compromise. Security guards and workers now help pick up litter and dissuade parking scofflaws.

Since then, 17 other stores have opened, and six more are coming in the next few weeks to Little Tokyo, Belmont Shore, Topanga Canyon, Beverly Hills, Lakewood and New York.

Competitors are vying for a piece of the success. Among the hatched frozen yogurt shops: Kiwiberry, Mr. Snowberry, Roseberry and Berri Good.

As a Pinkberry buzz has built, skeptics have questioned what's in it and whether it's as low-cal as it claims.

One customer said the hype reminded her of a famous "Seinfeld" episode in which Jerry and Elaine gain weight eating loads of "nonfat" yogurt. They finally test the yogurt only to discover that it's not really fat-free.

"I hope that episode wasn't foreshadowing Pinkberry's ending," one Angeleno wrote on the Giantrobot.com blog.

On Wednesday, Sandy Hsu, 26, a tourist from New Jersey, trekked to the Pinkberry store in Koreatown after a friend e-mailed her a photo of Paris Hilton spooning up the treat.

Hsu didn't seem to care what was in the icy concoction, but said it didn't live up to the hype: "It's not super good like I think I'd come back."

Regulars, though, said they were hooked.

"It just tastes good, and I'm not a frozen yogurt connoisseur by any means," said 19-year-old USC student Andrew Wilson.

Austin Cho, 27, agreed: "If it tastes like yogurt, I don't really care. Just as long as it's healthy."